1. Field of the Invention
The present invention relates to a dielectric resonator, and also to dielectric devices such as dielectric filters or duplexers composed therefrom.
2. Description of the Related Art
Such dielectric devices are used in high-frequency range such as sub-microwave band, microwave band, millimeter wave bands, and sub-millimeter wave band. More specific examples of applications include satellite communication devices, mobile communication devices, wireless communication devices, high-frequency communication devices, or base stations for such communication devices.
In conventional practice, resonators and dielectric filters used in portable phones and the like are commonly structured by combining a plurality of resonating components having one through-hole provided to a dielectric substarate, and the resonator length is commonly obtained by dividing a quarter of a wavelength xcex of the free space by the square root of the relative dielectric constant of the material constituting the dielectric substarate.
When composing a dielectric filter, either a plurality of resonators is connected by a separately prepared coupled circuit, or a plurality of through-holes is provided from one side to the exterior of an approximately rectangular dielectric substarate, the external surfaces excluding the open surface and the interiors of the through-holes are metallized, and the through-holes are fashioned into resonating components.
In the case of a dielectric filter that uses the dielectric substarate, an additional device such as a capacitor is added to the resonating component and a conductive pattern is formed on the open surface, yielding an additional element. Furthermore, by forming a groove, recess, or the like on the dielectric substarate itself, the balance of the electromagnetic coupling distribution is intentionally upset, and a configuration such as one coupled by an electric field or a magnetic field can be employed.
However, with conventional resonators and dielectric filters, when the goal is to shorten the resonator length in order to miniaturize the device, the load capacity must be formed separately, as described above, and configurations in which an additional device has been added to the resonator have a large number of components and are unsuitable for miniaturization.
Furthermore, with configurations in which a capacitor or the like is formed on the open surface of the resonator according to the conductor pattern, a complex and accurate conductive pattern must be formed on the open surface of the dielectric substarate, and miniaturization and height reduction will increase manufacturing costs and adversely affect the yield rate.
One of the features of the present invention is to provide a dielectric device suitable for miniaturization and height reduction.
Another feature of the present invention is to provide a surface-mountable dielectric device.
In order to achieve the above-described features, the dielectric device relating to the present invention comprises a dielectric substarate and at least one resonator unit. The dielectric substrate has an external conductor film on a first surface and other external surfaces.
The resonator unit comprises a first hole and a second hole. The first hole is provided to the dielectric substarate, has one end being open in the first surface, and extends from the first surface toward an external surface opposite thereto. The first hole has a first internal conductor in the interior, the first internal conductor being separated from the external conductor film on the first surface by a gap.
The second hole is provided to the dielectric substarate, has one end being open in an external surface not opposing the first surface, and is connected with the other end of the first hole in the interior of the dielectric substarate. The second hole also has a second internal conductor in the interior. One end of the second internal conductor is connected to the first internal conductor in the interior of the dielectric substarate, and the other end is connected to the external conductor film.
As described above, in the dielectric device relating to the present invention, the resonator unit comprises a first hole and a second hole, wherein a new hole configuration can be obtained in which the second hole intersects with the first hole at the other end opposing the open end.
In this new hole configuration, the first internal conductor provided to the first hole and the second internal conductor provided to the second hole are mutually connected.
Since the first internal conductor of the first hole faces the external conductor film via a dielectric layer composed of the dielectric substarate, a large electrostatic capacitance is generated between the first internal conductor film and the external conductor film. Therefore, the dielectric device relating to the present invention resonates at a frequency that is less than the electric length in relation to the length of the dielectric substarate, as seen from the axial direction of the second hole. In other words, miniaturization and height reduction can be achieved by shortening the length of the dielectric substarate in order to obtain the desired resonant frequency.
The dielectric device relating to the present invention can be used as an device with extensive coverage for a resonator, an oscillator, a dielectric filter, or a duplexer (also referred to as a antenna duplexer). The device may be completed with one resonator unit when used as a resonator. The device features a plurality of resonator units when used as a dielectric filter or duplexer.
When the device is used as a dielectric filter or duplexer, in addition to the length of the dielectric substarate being reduced for the aforementioned reasons, the interval between the first holes in two adjacent resonator units can be used to create capacitive coupling between the adjacent resonator units. Moreover, the capacitive coupling can be adjusted to the desired degree of coupling by adjusting the interval between the first holes in two adjacent resonator units. The electric coupling between adjacent resonator units can also be adjusted by either removing or adding conductors in the vicinity of the opening of the first internal conductor.
An inductive coupling can be substantially created between two adjacent resonator units using the capacitance between the first hole and the external conductor film provided to the dielectric substarate. This inductive coupling can also be adjusted to have the desired degree of inductive coupling by adjusting the interval between the first hole and the external conductor film provided to the dielectric substarate.
Furthermore, the device comprises a first terminal and a second terminal when used as a dielectric filter, and these terminals are used as input/output terminals. The first terminal can be provided at a position opposing the first hole provided to one of the resonator units via a dielectric layer of the dielectric substarate. The second terminal is provided at a position opposing the first hole provided to another resonator unit via a dielectric layer. Both the first and second terminals are insulated from the external conductor.
According to the previously described structure, the first and second terminals are capable of being mounted on a mount board. The first and second terminals may be provided to the external surface, provided to the first surface, or provided extending over two adjacent surfaces. Furthermore, the first and second terminals may be provided such that they form a capacitive coupling with the second internal conductor.
The device comprises at least three resonator units and first through third terminals when used as a duplexer. The first through third terminals are affixed to different resonator units and are used as an antenna connection terminal, a receiver terminal, and a transmitter terminal. According to the previously described structure, the first through third terminals are capable of being mounted on a mount board.
Additional objects, structures, and merits of the present invention are described in further detail with reference to the accompanying drawings. It is apparent, however, that the technological scope of the present invention is not limited to the illustrated embodiments.